Let builtin prints variables
Let builtin prints variables

After the refactoring of how let and other builtins were parsed, we
lost the ability to get a list of local variables just by supplying
the let command without any arguments. This will re-implement that
ability.

redox-os/ion,redox-os/ion,bheesham/ion,jwbowen/ion,redox-os/ion,jwbowen/ion,bheesham/ion